After 2 hours of camping to get 3 trinkets for twinks, my conclusion is:
(1) Trinket of the scale always drops.
(2) PH of Dranadune can be any of mist drakes and itself.
(3) No interval time between respawn, it can pop soon after just been killed.
So, for this camp what you should do after arriving is to check if Dranadune is up already.
If not, start killing all mist drakes, then kill steam drakes since they may repop as mist drakes next round.
I know it will pop soon after I killed 7-8 mist drakes in a round.
Edited, Sep 7th 2011 4:49am by zight